The present invention relates generally to improved bar code scanning and processing. More particularly, the invention relates to improved configurations and methods for compact dual aperture bar code scanning.
Bar code scanners are used in a wide variety of applications, notably retail checkout applications. Bar code scanners used in retail checkout applications appear in a wide variety of different configurations. A popular and useful configuration is a dual aperture scanner, which emits a scan pattern through each of two apertures, typically a generally horizontally oriented aperture and a generally vertically oriented aperture. A product is scanned by moving it so that it passes over the horizontal aperture and in front of the vertical aperture. In this way, a scan pattern emerging from the horizontal aperture illuminates one or more sides of the product and a scan pattern emerging from the vertical aperture illuminates one or more additional sides of the product. Thus, multiple sides of a product are illuminated, increasing the likelihood that a scan pattern emerging from one of the apertures will illuminate a bar code on the product and decreasing the likelihood that a product will need to be oriented in order to position a bar code to be scanned. Dual aperture scanners are typically capable of higher throughput than are single aperture scanners because single aperture scanners require more frequent orientation of items in order to bring barcodes on the items within the single scan pattern emitted by a single aperture scanner. Details of dual aperture scanners are disclosed in U.S. Pat. Nos. 6,059,189; 5,459,308 and 5,229,588, assigned to the assignee of the present invention and incorporated herein by reference in their entirety.
Scanned items are typically passed directly across the horizontal aperture, coming into physical contact with the horizontal aperture. Because items come into physical contact with the aperture, the material covering the aperture is subjected to considerable stress and therefore is typically made of an extremely durable material such as sapphire or diamond. Such materials are expensive, and therefore the horizontal aperture is typically relatively small. Scanned items are not typically brought into physical contact with the vertical aperture, and therefore the material covering the vertical aperture does not need to be as durable as that covering the horizontal aperture. The material covering the vertical aperture may suitably be made of an inexpensive material such as plastic, and the vertical aperture is therefore typically larger than the horizontal aperture.
A compact dual aperture scanner design would combine high throughput with the ability to be used in retail and other environments in which space is at a premium. However, many prior art scanner designs are not well adapted to being made compact, because of the placement of components in the scanner and because of the need to provide light paths which will produce desired scan patterns at the vertical and horizontal apertures.
There exists, therefore, a need for a dual aperture scanner which arranges components inside a compact volume in order to effectively use available space and to provide light paths to produce desired scan patterns at the horizontal and vertical apertures.
A dual aperture scanner according to one aspect of the present invention includes a horizontal cabinet section, or optics base, and a vertical cabinet section, or tower. The optics base includes a top surface and has a horizontal aperture within the top surface. The tower includes a front surface and has a vertical aperture within the front surface. An operator may suitably sit facing the vertical aperture so that the operator can pass items from left to right or right to left over the horizontal aperture and in front of the vertical aperture. The tower contains an optics engine, comprising electronics for light generation and detection, a rectangular spinner, a spinner motor and a set of primary mirrors, all mounted on a single mounting block. The optics engine includes a laser which emits a laser beam in a horizontal direction. The laser beam strikes a deflecting mirror which is preferably oriented 45 degrees from the horizontal. The deflecting mirror deflects the laser beam upward so that the laser beam strikes the spinner. The spinner has four facets, aligned at different angles. As the spinner rotates, the laser beam strikes and is reflected by the first, second, third and fourth facets in order. The spinner scans the laser beam to produce fans of rays which are reflected from the spinner in directions determined by the orientation of the spinner and by the angles of the facets from which the rays are reflected. The facets of the spinner are oriented at different angles, so that they can reflect the laser beam so as to produce rays having different directions. The first and third facets both reflect the laser beam so as to produce rays oriented downward and toward the vertical aperture, that is, toward the front of the scanner, and the second and fourth facets both reflect the beam to as to produce rays oriented downward and away from the vertical aperture, or toward the rear of the scanner. The rays are directed toward primary pattern mirrors. The primary pattern mirrors further reflect the rays to secondary mirrors. The secondary mirrors reflect the rays through the horizontal and vertical apertures and out of the scanner to produce a scan pattern emerging from each aperture. The rays initially travel away from the spinner, but the mirrors are oriented such that some of the rays are reflected back in the direction of the spinner and follow paths which take them in close proximity to the spinner in order to follow a path leading from the spinner to the primary and secondary mirrors to which they are directed and from the secondary mirrors to the correct aperture. Orienting the mirrors so that rays are directed to travel in the proximity of the spinner effectively uses space near the spinner in order to provide desired path lengths for the rays and allows greater flexibility in designing scan patterns.
When a scan pattern strikes a bar code outside the scanner, a portion of the light making up the scan pattern is scattered and is reflected back into the scanner in an expanding cone centered on the incident laser beam. The scattered light passes through the apertures and strikes in turn the various secondary mirrors, primary mirrors and the spinner, where it is de-scanned. The de-scanned light strikes a collection lens, where it is focused and directed toward a photodetector. The deflecting mirror reflects the collected light onto the photodetector. The photodetector produces a photosignal which can be processed to extract the bar code information.
A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following Detailed Description and the accompanying drawings.